Albert Barnes Commentary Ecclesiastes 4:7-12

"Then I returned and saw vanity under the sun. There is one that is alone, and he hath not a second; yea, he hath neither son nor brother; yet is there no end of all his labor, neither are his eyes satisfied with riches. For whom then, [saith he], do I labor, and deprive my soul of good? This also is vanity, yea, it is a sore travail. Two are better than one, because they have a good reward for their labor. For if they fall, the one will lift up his fellow; but woe to him that is alone when he falleth, and hath not another to lift him up. Again, if two lie together, then they have warmth; but how can one be warm [alone]? And if a man prevail against him that is alone, two shall withstand him; and a threefold cord is not quickly broken." — Ecclesiastes 4:7-12 (ASV)

The spectacle of a prosperous man whose condition is rendered vain by his brotherless, childless isolation (Ecclesiastes 4:8).

A second—anyone associated or connected with him (Ecclesiastes 4:9–12).

Compare a saying from the Talmud: “A man without companions is like the left hand without the right.”